A subsea control umbilical may be employed to connect remotely positioned subsea satellite production and/or injection christmas trees to subsea template controls or to surface controls on a platform loading production vessel. Subsea control umbilicals are also employed to connect several small subsea templates together before ascending to the surface platform or vessel. A riser bundle or umbilical can include up to eighteen separate control hoses within a casing. The casing may include an armor outer surface to protect the enclosed control hoses. The umbilicals are usually supported by wire cables for strength.
The distances between subsea systems may range from a few hundred feet to as much as ten to twenty miles. The subsea control umbilical connecting subsea christmas trees and templates together are subject to damage by vessel mooring lines and anchors, fishing vessels using trawling boards, subsea mudslides and ocean floor drift. The most common damage to such subsea systems is caused by mooring lines or anchors snagging the subsea control umbilical and supporting cables and pulling against the christmas tree, template termination or riser base. The loads on such subsea systems are extreme when the subsea control umbilical and supporting cables are snagged by anchors and pulled away. The breaking strength of the umbilical armor and supporting cables may range from 30,000 pounds to 80,000 pounds, depending upon the wire gauge and material strength, and is more than enough to cause severe damage to the subsea systems.
The riser bundle or umbilical preferably includes a safety joint which will separate when a predetermined tension on the umbilical is exceeded. Typically such safety joints employ "weak link" bolts as connection means which are designed to break when a predetermined tension is exceeded to allow separation of the armor casing and the support cables. Upon separation of the weak link bolts, the inner control hoses are typically allowed to break under the tension. Often, the control hose connections can be damaged during such tension failure. Further, the separation of the control hoses due to such tension failure is not a predictable occurrence and control hose segments other than in the area of eventual failure can be weakened by stretching.